Isospin and mixed symmetry structure in 24Mg

The interacting boson model with isospin (IBM-3) has been used to study the isospin excitation states and electromagnetic transitions for ²⁴Mg nucleus. The mixed symmetry states at low spin are also analyzed. The theoretical calculations are in agreement with experimental data. The present calculations indicate that the 3₁⁺ state is the lowest mixed symmetry state.     

Mixed Symmetry Isomeric States in Nuclei

Mixed symmetry states are studied in the framework of the neutron-proton interacting boson model.It is found that some of the mixed symmetry states with moderate high spins change very fast with respect to the Majorana interaction.Under certain conditions,they become the yrast state or yrare state.These states are difficult to decay and become very stable.This study suggests that a possible new mode of isomers may exist due to the special nature in their proton and neutron degrees of freedom.     

Level Schemes in Neutron-Rich 141Xe、152Ce、153Nd and 160Sm Nuclei

The level schemes of neutron-rich nuclei,¹⁴¹Xe、¹⁵²Ce、¹⁵³Nd and ¹⁶⁰Sm have been established for the first time through measuring the prompt γ-rays from spontaneous fission of ²⁵²Cf.The highest spin state is up to 16⁺.The collective band structures in these neutron-rich nuclei are discussed.     

Mixed Symmetry States in Even—Even ^96—108Mo Nuclei

Excitation energies and electromagnetic transition strengths in even-even ^96-108Mo nuclei have been described systematically be using the proton-neutron interacting boson model (IBM-2).It appears that the properties of low-lying levels in these isotopes,for which the comparison between experiment and theory is possible,can be satisfactorily described by the IBM-2 model,provided proper account is taken of the presence at low energy of states having a mixed-symmetry character.It seems possible to identify,in each isotope,a few states having such a character,the lowest ones being either 22^ or 23^ levels.It is found that these nuclei are in the transition from U(5) to SU(3).     

Complex Fragments Emitted in Reactions of 46．7MeV/u 12C on 197Au,115In and 58Ni

Energy spectra of complex fragments emitted in the reactions of 46.7MeV/u ¹²C with different targets ¹⁹⁷Au,¹¹⁵In and ⁵⁸Ni have been measured by telescopes,consisting of a gis ionization counter followed by a position Sensitive semiconductor detector.Tha most probable kinematical energies.E_p of complex fragments and temperature parameters of long－live intermediate systems have been deduced by complex fragment ernergy spectra.The experimental values of E_p are lower than the calculated ones by E=V_coul+2T.The experimental values of complex fragment yields can be reproduced by simple A.Friedman statistical evaporation model satisfactorily.     

(EC/β+) Decay of 130Nd and 140Tb

Isotopes,¹³⁰Nd and ¹⁴⁰Tb were produced using enriched targets ⁹⁶Ru and ¹⁰⁶Cd, respectively,bombarded by ³⁶Ar ion beam. The two nuclides were identified and studied by a He-jet tape transport system in combination with "X-γ" and "γ-γ" coincidence measure- ments. The half-life of ¹³⁰Nd was determined to be (13±2)s. The EC/β⁺ decay scheme of 130Nd was proposed for the first time, and the spins and parties of the ground-state and observed low-lying states in the daughter nucleus ¹³⁰Pr were speculated tentatively. The previous simple EC/β⁺ decay scheme of ¹⁴⁰Tb was revised, and the spin-parity of its groundstate was assigned to be 7⁺.     

Nuclear Structure in Lead Region(I) Energy Spectra and Wavefunctions of 207—210T1 and 207,208Hg

The energy spectra and wavefunctions of ^207—210T1 and ^207,208Hg are calculated in terms of shell model.The calculated results using different effective interactions are similar and agree well with experimental data,which shows that those effective intemcdons widly used in lead region are still valid to describe the energy levels for nuclei such as ²⁰⁸T1 etc.     

Electron Spin Pairing and Excitations in High—Tc Superconductors

Effective spin coupling between conduction electrons mediated by local Cu moments in the doped CuO2 plane may induce the instability of the normal states of conduction electrons and pairing at Cu stes,where the superexchange interaction between local moments influenced by hole doping has been found to be Ising-like in recent experiments.By a mean field approach,we show that spin pairing and strong pair-pair interaction in the doped antiferromagnetic ordered Ising-like CuO2 plane gives rise to high-temperature superfluid condensation and the exceptional features of quasi-particle excitation in cuprates such as spin gap,pseudogap,and the linear temperature dependence of resistivity ρab in the normal states.     

(EC+β+) Decay of 130Pm and 128Pr

¹³⁰Pm and ¹²⁸ Pr were produced by irradiation of ⁹⁶Ru with 171MeV ³⁶Ar beam,and a He-jet recoil tape transport system transported radioactivities to shielded reigon. Based on X-γ-t and γ-γ-t coincidence measurements ,the (EC+β⁺)decay scheme of ¹³⁰Pm was proposed for the first time and the (EC+β⁺)decay scheme of ¹²⁸Pr was revised.     

Study on Stiffness of the Symmetry Energy at High Densities by π－/π+ Ratio

using the isospin–and momentum–dependent transport model, for three different symmetry energies, we have calculated the π^–/π⁺ ratio as a function of time and tranverse–momentum in central 132sn+124 sn collision at e_beam/A=400mev. the results show that the π^–/π⁺ ratios is very sensitive to the stiffness of the symmetry energy. thus we can probe the stiffness of the symmetry energy at high densities by using the π–/π+ ratio at different time or transverse momentum more accurately than before. comparing experimental data with the calculations will reveal crucial information about the stiffness of the symmetry energy more accurately.hadronic transport model, symmetry energy, π–/π+ ratio     

β-Delayed Proton Decays of 133Sm and 149Yb

¹³³Sm was produced via fusion evaporation in the reaction ⁴⁰Ca+⁹⁶Ru. Its β-delayed proton decay was studied by means of “p-γ” coincidence in combination with a He-jet tape transport system, including half-lives, proton energy spectra, γ-transitions following the proton emissions, and the branching ratios to the low-lying states in the grand-daughter nuclei. The possible spins and parities of ¹³³Sm were extracted by fitting the experimental data with a statistical model calculation. The configuration-constrained nuclear potential energy surfaces of ¹³³Sm were calculated by using the Woods-Saxon Strutinsky method. Comparing the experimental and calculated results, the spins and parities of ¹³³Sm were assigned to be 5/2⁺ and 1/2^－, which is reconciled with our published simple (EC+β⁺) decay scheme of ¹³³Sm in 2001. In addition, our experimental data on the beta-delayed proton decay of ¹⁴⁹Yb reported in Eur. Phys. J., 2001, A12: 1—4 was also analyzed by using the same method. The spin and parity of ¹⁴⁹Yb was assigned to be 1/2^－.     

Isospin and F-spin symmetry structure in low-lying levels of 48，50Cr isotopes

The low-energy level structure and electromagnetic transitions of ^48.50Cr nuclei have been studied using the interacting boson model with isospin (IBM-3). A sequence of isospin excitation bands with isospin T = Tz, Tz 1and Tz 2 has been assigned, and compared with available data. According to this study, the 2^3 and 2^2 states are the lowest mixed symmetry states in ^48Cr and ^50Cr, respectively. In particular, the present calculations suggest that a combination of isospin and F-spin excitation can explain the structure in these nuclei. The transition probabilities between the levels are analysed in terms of isoscalar and isovector decompositions which reveal the detailed nature of the energy levels. The results obtained are in good agreement with recent experimental data.     

The Study of α Emission Induced by 46.7MeV/u 12C on 58Ni、115In and 197Au

The energy spectra and angular distribution of α particles emitted from ¹²C induced reactions with ⁵⁸Ni,¹¹⁵In and ¹⁹⁷Au have been measured.Three moving sources of emitting α particle are clearly seen from invariant cross section distribution in velocity coordinates.The experimental data were analyzed by using three moving sources.Extracted parameters of the source with half-beam velocity are in agreement with the systematic values from Fermi Gas Model.The energy spectra and the extracted parameters for various targets are discussed.The low energy peak in energy spectra is possibly from the emitted α particle from equilibrium system after pre-equilibrium emission of target-like products.The energetic α particles are mainly from projectile fragmentation and projectile-like fragmentation.     

β-Delayed Proton Decays of 140Tb and 141Dy as Well as the Spin and Parity of 143Dy

¹⁴⁰Tb and ¹⁴¹Dy were produced via fusion evaporation in the reaction ⁴⁰Ca+¹⁰⁶Cd. Their β-delayed proton decays were studied by means of “p-γ” coincidence in combination with a He-jet tape transport system, including half-lives, proton energy spectra, γ-transitions following the proton emissions, and the branching ratios to the low-lying states in the grand-daughter nuclei. The ground-state spins and parities of 140Tb and 141Dy were extracted as 7^± and 9/2^±, respectively, by fitting the experimental data with a statistical model calculation. The configuration-constrained nuclear potential energy surfaces (NPES) of ¹⁴⁰Tb and ¹⁴¹Dy were calculated by using the Woods-Saxon Strutinsky method, which indicate the ground-state spins and parities of ¹⁴⁰Tb and ¹⁴¹Dy to be 7⁺and 9/2^－, respectively. In addition, the configuration-constrained NPES of ¹⁴³Dy was also calculated by using the same method. From the NPES a 1/2⁺ ground state and a 11/2^－ isomer with the excitation energy of 198keV were found. The calculated results are consistent with our experimental data on the decay of ¹⁴³Dy reported in Eur. Phys. J., 2003, A16: 347—351.     

Low-Lying Spectra and Electromagnetic Transition Rates in 140—162Gd in the Interacting Boson Model

Spectra and electromagnetic transition for the even-even ^140—162Gd isotopes are studied in the framework of the interacting boson model. A schematic Hamiltonian can be used to describe their spectra and transition. The results show that ^140—162Gd are in the transition from the vibrational limit to rotational limit.     

Hypernuclear Magnetic Moments and λ--N Interaction in 17λO

Hypernuclear magnetic moment and λ--N interaction in ¹⁷_λO has been studied within relativistic mean field theory. Without core polarization, the relativistic results are found to fit the Schmidt value well and not be sensitive to λ--N interaction. The relativistic magnetic moment is enhanced with nearly equal contributions of the relativistic and free masses. When λ hyperon occupies the l=0 or l=1 orbit, the effect of λ--N interaction on the magnetic moment of valence proton is different.     

Mixing of two-quasineutron and two-quasiproton Kπ=6+ configurations in the vicinity of 174Yb

In the framework of the projected shell model, we investigate the competition between the two-quasineutron and two-quasiproton K^π=6⁺ states in the ytterbium isotopes and N =104 isotones adjacent to ¹⁷⁴Yb. The ¹⁷⁴Yb results are compared with the experimental data.The K^π =6⁺ isomer observed in ¹⁷⁴ Yb is assigned as an admixture of the ν7/2^-[514] ν5/2^-[512] and π7/2⁺ [404]π5/2⁺ [402] intrinsic structure, which explains the experimental |g K-g R | value. Similar mixing would appear in ¹⁷⁴ Yb, ¹⁷⁶ Hf,and ¹⁷⁸ W. The low-lying K^π=6⁺ states are also predicted in ^170-178 Yb.     

12C+27Al,12C+209Bi和14N+Pb反应全熔合截面测量

本文叙述了用云母径迹探测器分别探测复合核蒸发余核和裂变碎片的实验,从而测出了¹²C+²⁷Al,¹²C+²⁰⁹Bi和¹⁴N+Pb反应的全熔合截面和激发函数.并用锐截止模型由全熔合截面导出了临界角动量.实验结果和当前有关的理论计算进行了比较,在实验误差范围内基本相符.     

(EC+β+) Decay of 133Sm and 1.1s Isomer of 133Pr

By irradiation of an enriched target of ⁹⁶Ru with ⁴⁰Ca and using a helium-jet fast tape transport system in combination with X-γ and γ-γ coincidence measurements,the very neutron deficient isotope ¹³³Sm was produced and studied. A simple(EC+β⁺) decay scheme of Sm is proposed for the first time. A by product ¹³³Pr was produced simultaneously because of the ^98－102Ru contents of the ruthenium target. The half-life of an 11/2^－ low-lying isomeric state in ¹³³Pr has been measured to be (1.1±0.2)s. Using single-particle model,the reduced transition probabilities of the 11/2^－ isomers in ^{131,133,135,137}Pr are extracted from their experimental half-lives and compared with the Weisskopf estimate.